Drilling motors, or mud motors, are included in a drill string to provide additional rotational force to a drill bit while drilling. Mud motors use the hydraulic force of drilling fluid, or drilling mud, sent down hole through the drilling motor to drive its rotation. Particularly, the drilling fluid is passed through at least one stage consisting of a stationary stator vane, which is coupled to the drill string, and a rotating rotor assembly, which is coupled to a drive shaft of the drill string. The vanes of the stator are commonly configured to direct the drilling fluid into the rotor vanes. The rotor vanes then impart rotation to the drive shaft, which provides an additional driving force for to drill bit.
Mud motors are characterized by a high speed or rotations per minute (“RPM”) to torque ratio. As a result, the drive shaft of the motor may experience high bending loads during operation. In some cases, this high bending load may result in a down hole failure. In the event of a down hole failure, the drive shaft may fracture and result in a lower end of the drive shaft parting from the working section of the drive shaft. In such a situation, a catch device may be necessary to prevent losing the lower end of the drive shaft down hole.
U.S. Pat. No. 8,025,110 discloses a catch device having a sleeve secured to a portion of the output shaft and an interference structure that is secured to the general housing. The interference structure extends into the capture groove and is configured to secure the sleeve and output shaft in an event of a lower end of the output shaft parting from the rest of the output shaft.
U.S. Patent App. 2010/0314172 discloses a locking clutch and catch device for a down hole motor. The catch device includes a spacer secured to the drive shaft with a flange that extends radially outward to trap a lip of a mandrel stabilizer that extends radially inward in the event of the lower end of the drive shaft parting from the rest of the output shaft.